Author Topic: MS460 starts then dies  (Read 702 times)

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Offline bassman

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MS460 starts then dies
« on: February 06, 2013, 11:11:56 am »
i havea Ms460 that starts and runs for about 5 seconds then dies. I havent replaced the diaphrams in the carb. they
 seem to be ok. Could the carburetor be faulty?

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Offline 660magnum

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Re: MS460 starts then dies
« Reply #1 on: February 06, 2013, 12:28:27 pm »
The metering diaphragm can cause erratic fuel mixture problems because it is stiff. The integrity of the diaphragm will be complete but the carb will not work correctly.
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Offline Energo70

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Re: MS460 starts then dies
« Reply #2 on: February 06, 2013, 03:50:49 pm »
I would look for ragged sucking tube between cylinder and carburetor or impulse tube.

Offline bassman

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Re: MS460 starts then dies
« Reply #3 on: February 06, 2013, 05:02:53 pm »
I did a pressure check on the saw and found no leaks. When the saw quits it will start right back up again. Runs great for a few seconds. Its like someone shuts the switch off.

Offline Al Smith

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Re: MS460 starts then dies
« Reply #4 on: February 06, 2013, 05:52:21 pm »
A stiff main diaphragm can often get the saw started but very quickily run itself out of fuel once the thing is running .Because of being stiff it's capacity to hold fuel is diminished .

Fact just today I had a very similar situation on a 2 cycle snow blower .The thing did have electric start which saved my arm .I set it extremely rich where it would idle and blow black smoke .After a while it had limbered up the diaphragm enough it would run under normal conditions .I'll bet it took a dozen -15 restarts and ten minutes of running before it healed its self .

Offline 660magnum

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Re: MS460 starts then dies
« Reply #5 on: February 06, 2013, 06:48:52 pm »
With the choke closed, the engine itself can suck fuel all the way through a carburator regardless of the metering diaphragm but the carb will not function on its own because of a bad pump valve or a stiff diaphragm.
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Offline bassman

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Re: MS460 starts then dies
« Reply #6 on: February 08, 2013, 03:42:52 pm »
I put new diaphrams in the carb. It still starts then dies. I am soaking carburetor again and see if that helps. Im thinking carb might need replaced. Thanks for your help.  Any other ideas , Im all ears.

Offline 660magnum

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Re: MS460 starts then dies
« Reply #7 on: February 08, 2013, 04:42:42 pm »
You may have trouble with the impulse line or path or a hole in the impulse line

There may be a hole in the fuel line

Or the fuel filter may be plugged
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Offline Al Smith

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Re: MS460 starts then dies
« Reply #8 on: February 08, 2013, 08:14:47 pm »
It's probabley a better practice to change all the soft componets of a the carb instead of just the main diaphragm providing you have them all .Usually if the main gets stiff so are the fuel pump checks .

Now I'll admit I've gone through my pile of junk a time or two and found some componets that did work but they were short lived .

Offline darren_palms

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Re: MS460 starts then dies
« Reply #9 on: February 09, 2013, 12:13:49 pm »
It's probabley a better practice to change all the soft componets of a the carb instead of just the main diaphragm providing you have them all .Usually if the main gets stiff so are the fuel pump checks .

Now I'll admit I've gone through my pile of junk a time or two and found some componets that did work but they were short lived .

I agree, sometimes changing the all the carb compenents could fix it.

 

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